CN111019720B - Green production process of biodiesel - Google Patents
Green production process of biodiesel Download PDFInfo
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- CN111019720B CN111019720B CN201911408487.6A CN201911408487A CN111019720B CN 111019720 B CN111019720 B CN 111019720B CN 201911408487 A CN201911408487 A CN 201911408487A CN 111019720 B CN111019720 B CN 111019720B
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L1/00—Liquid carbonaceous fuels
- C10L1/02—Liquid carbonaceous fuels essentially based on components consisting of carbon, hydrogen, and oxygen only
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- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
- C11C1/00—Preparation of fatty acids from fats, fatty oils, or waxes; Refining the fatty acids
- C11C1/08—Refining
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- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
- C11C1/00—Preparation of fatty acids from fats, fatty oils, or waxes; Refining the fatty acids
- C11C1/08—Refining
- C11C1/10—Refining by distillation
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- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
- C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
- C11C3/003—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fatty acids with alcohols
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- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
- C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
- C11C3/04—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fats or fatty oils
-
- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
- C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
- C11C3/04—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fats or fatty oils
- C11C3/10—Ester interchange
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/10—Biofuels, e.g. bio-diesel
Abstract
The invention discloses a green production process of biodiesel, which comprises the following steps: (1) pre-esterification; (2) performing esterification reaction; (3) performing ester exchange reaction; (4) flash evaporation dealcoholization; (5) washing with water; (6) deodorizing; (7) distilling; conveying the acid residue water and the crude glycerol to a neutralization kettle together for neutralization reaction, evaporating methanol after the neutralization is finished, and conveying the evaporated methanol to a methanol rectifying tower; adding concentrated sulfuric acid to adjust the pH value of the neutralized product after the methanol removal to 6-6.5, standing for layering, allowing the glycerol at the lower layer to enter a glycerol storage tank, and allowing the acidified oil at the upper layer to enter a waste oil storage tank to be reused as a raw material. The invention can effectively remove impurities in the raw materials, reduce the production pressure of the subsequent process, improve the product quality, recycle acid sludge water and saponified oil, and reduce the environmental protection pressure and the production cost.
Description
Technical Field
The invention relates to the technical field of biodiesel production, in particular to a green production process of biodiesel.
Background
The biodiesel oil is fatty acid methyl ester or ethyl ester prepared by ester-converting vegetable oil (such as oleum Rapae, soybean oil, peanut oil, corn oil, cottonseed oil, etc.), animal oil (such as fish oil, lard, beef tallow, mutton fat, etc.), waste oil or microbial oil with methanol or ethanol. Biodiesel is a typical 'green energy source', and has the characteristics of good environmental protection performance, good engine starting performance, good fuel performance, wide raw material source, renewability and the like. The vigorous development of the biodiesel has important strategic significance on economic sustainable development, energy source replacement promotion, environmental pressure reduction and urban atmospheric pollution control.
In recent years, many researches prove that the hydrocarbon is reduced by 55-60%, the particulate matter is reduced by 20-50%, the CO is reduced by more than 45%, and the polycyclic aromatic hydrocarbon is reduced by 75-85% after the biodiesel is combusted no matter the diesel engine is a small-sized and light-duty diesel engine or a large-sized and heavy-duty diesel engine or a tractor.
The acid-base two-step catalysis method has wide sources and low requirements on raw materials because the raw materials of the method are mainly animal and vegetable oil, particularly waste oil of kitchens can be used as the raw material, the waste oil can be reutilized, the chance of the waste oil returning to dining tables can be reduced, and simultaneously, the oil cannot compete with people, so that most biodiesel enterprises in China adopt the production method. A large amount of acid residue water is generated in the esterification process, the acid residue water comprises water, sulfuric acid and acidified oil (accounting for about 6% of the weight of the raw oil), the acid residue water is difficult to treat and high in treatment cost, and the acid residue water can bring out part of oil raw materials, so that the raw materials are wasted. In the ester exchange process, part of the oil is saponified under alkaline conditions, and the saponified oil is mixed in the glycerol to reduce the purity of the glycerol, and at the same time, the oil (about 3% of the weight of the raw oil) is wasted. How to economically and effectively solve the problems of acid residue water treatment and saponified oil recovery becomes a great problem to be solved urgently by various biodiesel enterprises.
In addition, how to effectively remove impurities in the raw materials, reduce the production pressure of the subsequent process, improve the utilization rate of the raw materials and the quality of products also needs to be solved.
Disclosure of Invention
The invention aims to provide a green production process of biodiesel, which can effectively remove impurities in raw materials, reduce the production pressure of subsequent processes, improve the product quality, recycle acid sludge water and saponified oil, and reduce the environmental protection pressure and the production cost.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a green production process of biodiesel comprises the following steps:
(1) pre-esterification: sequentially inputting methanol, concentrated sulfuric acid and waste oil into a reaction kettle, heating the reaction kettle while stirring when the waste oil is input, and blowing the residual waste oil in the pipeline into the reaction kettle by using compressed air so as to prevent the pipeline from being blocked after the waste oil is input; controlling the oil temperature in the reaction kettle at 60-65 ℃, reacting at low temperature for 110-130min, standing for 30-40min, opening a valve at the bottom of the reaction kettle to discharge acid residue water, and collecting the acid residue water to enter an acid residue water storage tank;
(2) esterification reaction: heating the oil temperature in the reaction kettle to 100-plus 105 ℃, starting to supplement methanol into the reaction kettle under the stirring condition, controlling the oil temperature to be between 108-plus 112 ℃ in the methanol supplementing process until the acid value of the oil in the reaction kettle is less than 3mgKOH/g, cooling, stopping supplementing the methanol, opening a valve at the bottom of the reaction kettle to discharge acid residue water, collecting the acid residue water, and feeding the acid residue water into an acid residue water storage tank;
(3) ester exchange reaction: when the temperature of oil in the reaction kettle is reduced to 80-85 ℃, adding methanol alkali into the reaction kettle, wherein the methanol alkali is formed by mixing sodium hydroxide and methanol, controlling the temperature of grease to be 65-70 ℃, carrying out ester exchange reaction for 1.5-2 hours under the condition of stirring, stopping stirring after the reaction is finished, separating a reaction product to obtain crude glycerol and crude methyl ester, and feeding the crude glycerol into a crude glycerol storage tank;
(4) flash evaporation dealcoholization: the crude methyl ester enters a flash evaporator for flash evaporation and methanol removal, and the temperature of the flash evaporation and methanol removal is controlled to be 75-80 ℃;
(5) washing with water: feeding the crude methyl ester subjected to flash evaporation and dealcoholization into a water washing tank, controlling the temperature of the crude methyl ester to be 70-75 ℃ during water washing, standing for 2-3 hours for layering, and discharging a lower water layer;
(6) deodorizing: deodorizing the washed crude methyl ester in a deodorizer;
(7) and (3) distillation: the deodorized crude methyl ester enters a methyl ester distillation tower for distillation, and the distilled methyl ester is condensed by a condenser to obtain a finished product of the biodiesel;
collecting methanol overflowing from the top of the reaction kettle in the step (1) to the step (3) and methanol overflowing from the top of the flash evaporator in the step (4) to a methanol rectifying tower, rectifying and condensing the methanol in the methanol rectifying tower to obtain methanol with the concentration of more than 98 percent, and sending the methanol to a methanol raw material tank to be reused as the methanol raw material in the step (1) to the step (3);
conveying the acid residue water in the acid residue water storage tank in the step (1) and the crude glycerin in the crude glycerin storage tank in the step (3) to a neutralization kettle for neutralization reaction, evaporating methanol after the neutralization is finished, and conveying the evaporated methanol to a methanol rectifying tower; adding concentrated sulfuric acid to adjust the pH value of the neutralized product after the methanol removal to 6-6.5, standing for layering, allowing the glycerol at the lower layer to enter a glycerol storage tank, and allowing the acidified oil at the upper layer to enter a waste oil storage tank to be reused as a raw material.
Aiming at the problem of a large amount of acid sludge water generated in the esterification reaction process (including pre-esterification), the inventor researches and develops a smart treatment mode, and in consideration of the particularity of large acidity of the acid sludge water, the inventor seeks a solution in the production process, the ester exchange reaction adopts strong base as a catalyst, and a large amount of alkaline glycerol is generated after the reaction, so the acid sludge water generated in the esterification reaction process and the alkaline glycerol generated after the ester exchange reaction are neutralized, an additional acid-base substance is not required to be utilized, the neutralization product methanol can be removed, methanol can be recycled as a raw material, the acidified oil and the glycerol can be separated after the neutralization product methanol is slightly acid-removed, the waste oil of the reaction raw material needs to be added with acid for catalysis, and therefore, the acidified oil can be reused as the raw material, so the oil brought out from the acid sludge water can be effectively utilized, thereby improving the utilization rate of the raw materials. In addition, the crude glycerin separated from the ester exchange reaction contains saponified oil, and the oil is neutralized with acid residue water and is reduced into fatty acid after acidification, and the fatty acid is separated and reused as a component of acidified oil.
Because the raw materials of the waste grease have different quality and larger impurity fluctuation, in order to better adapt to different states of the raw materials and effectively remove impurities in the raw materials, the invention sets a pre-esterification operation before formal esterification reaction, and can basically clear the impurities through specific low-temperature pre-esterification reaction, so that the subsequent esterification reaction is not influenced, thereby reducing the production pressure of the subsequent process and improving the product quality.
In the step (1), the using amount of the methanol is 18-20% of the weight of the waste oil.
In the step (1), the dosage of the concentrated sulfuric acid is 0.3-0.8% of the weight of the waste grease.
In the step (2), the flow rate of methanol is controlled to be 300-700L/h during methanol supplement. The flow rate of the alcohol supplement cannot be too small, and the reaction time is easily prolonged when the flow rate is too small; the flow can not be too large, and the temperature of the tank body can be quickly reduced due to too large flow, so that the reaction can be influenced, and the reaction time can be prolonged.
In the step (3), the dosage of the methanol is 15-20% of the weight of the waste oil, and the dosage of the sodium hydroxide is 0.3-0.7% of the weight of the waste oil.
In the step (3), the pH of the ester exchange reaction is controlled to be 7.5-8.
In the step (5), the dosage of washing water is 15-20% of the weight of the crude methyl ester, the water temperature is 80-85 ℃, and the washing time is 15-20 min.
In the step (7), the methyl ester distillation is carried out under the negative pressure which is controlled to be more than-0.095 MPa.
In step (7), the methyl ester distillation temperature is 215-235 ℃.
The invention has the beneficial effects that: the method can effectively remove impurities in the raw materials, reduce the production pressure of the subsequent process, improve the product quality, recycle acid sludge water and saponified oil, and reduce the environmental protection pressure and the production cost.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The technical solution of the present invention will be further specifically described below by way of specific examples.
In the present invention, the raw materials and equipment used are commercially available or commonly used in the art, unless otherwise specified. The methods in the following examples are conventional in the art unless otherwise specified.
Example 1:
the green production process of the biodiesel shown in figure 1 comprises the following steps:
(1) pre-esterification: sequentially inputting methanol, concentrated sulfuric acid (98% sulfuric acid, commercially available) and waste oil (swill-cooked dirty oil) into a reaction kettle, heating the reaction kettle while stirring when inputting the waste oil, and blowing the residual waste oil in a pipeline into the reaction kettle by using compressed air after the input of the waste oil is finished so as to prevent the pipeline from being blocked; controlling the oil temperature in the reaction kettle at 60 ℃, reacting at a low temperature for 130min, standing for 30min, opening a valve at the bottom of the reaction kettle to discharge acid residue water, and collecting the acid residue water to enter an acid residue water storage tank; in the step, the using amount of the methanol is 18% of the weight of the waste oil, and the using amount of the concentrated sulfuric acid is 0.3% of the weight of the waste oil;
(2) esterification reaction: heating the oil temperature in the reaction kettle to 100 ℃, starting to supplement methanol into the reaction kettle under the stirring condition, controlling the flow rate of the methanol to be 300L/h, controlling the oil temperature to be about 110 ℃ in the methanol supplementing process, starting to detect the acid value after supplementing the methanol for half an hour, detecting once every half an hour until the acid value of the oil in the reaction kettle is less than 3mgKOH/g, cooling, stopping supplementing the methanol, opening a valve at the bottom of the reaction kettle to discharge acid residue water, and collecting the acid residue water to enter an acid residue water storage tank; generally, 3.5 to 4 hours are needed from the beginning of alcohol supplement to the end of esterification;
(3) ester exchange reaction: when the temperature of oil in the reaction kettle is reduced to 80 ℃, adding methanol alkali which is formed by mixing sodium hydroxide and methanol into the reaction kettle, controlling the temperature of oil to be 65 ℃, and carrying out transesterification reaction for 2 hours under the stirring condition, wherein the pH value of the transesterification reaction is controlled to be 7.5-8; after the reaction is finished, stopping stirring, separating the reaction product to obtain crude glycerol and crude methyl ester, and feeding the crude glycerol into a crude glycerol storage tank; in the step, the using amount of the methanol is 15 percent of the weight of the waste oil, and the using amount of the sodium hydroxide is 0.3 percent of the weight of the waste oil;
(4) flash evaporation dealcoholization: the crude methyl ester enters a flash evaporator for flash evaporation and methanol removal, and the temperature of the flash evaporation and methanol removal is controlled at 75 ℃;
(5) washing with water: feeding the crude methyl ester subjected to flash evaporation and dealcoholization into a water washing tank, controlling the temperature of the crude methyl ester to be 70 ℃ during water washing, controlling the using amount of water for water washing to be 15 percent of the weight of the crude methyl ester, controlling the water temperature to be 80 ℃, and carrying out water washing for 20 min; standing for 2 hours for layering, and discharging a lower water layer;
(6) deodorizing: deodorizing the washed crude methyl ester in a deodorizer;
(7) and (3) distillation: distilling the deodorized crude methyl ester in a methyl ester distillation tower, controlling the temperature at the bottom of the tower to be 235 ℃, the temperature at the middle part of the tower to be 215 ℃, the temperature at the top of the tower to be 100 ℃, and the vacuum degree to be 0.095Mpa, condensing the distilled methyl ester by a condenser to obtain a finished product of the biodiesel, wherein the acid value of the finished product is 0.35mgKOH/g, and the yield is 88%;
collecting methanol overflowing from the top of the reaction kettle in the step (1) to the step (3) and methanol overflowing from the top of the flash evaporator in the step (4) to a methanol rectifying tower, rectifying and condensing the methanol in the methanol rectifying tower to obtain methanol with the concentration of more than 98 percent, and sending the methanol to a methanol raw material tank to be reused as the methanol raw material in the step (1) to the step (3);
conveying the acid residue water in the acid residue water storage tank in the step (1) and the crude glycerin in the crude glycerin storage tank in the step (3) to a neutralization kettle for neutralization reaction, evaporating methanol after the neutralization is finished, and conveying the evaporated methanol to a methanol rectifying tower; adding concentrated sulfuric acid to adjust the pH value of the neutralized product after the methanol removal to 6-6.5, standing and layering for about 5 hours, wherein the lower layer of glycerol enters a glycerol storage tank, and the upper layer of acidified oil enters a waste oil storage tank to be reused as a raw material.
Example 2:
the green production process of the biodiesel shown in figure 1 comprises the following steps:
(1) pre-esterification: sequentially inputting methanol, concentrated sulfuric acid (98% sulfuric acid, commercially available) and waste oil (swill-cooked dirty oil) into a reaction kettle, heating the reaction kettle while stirring when inputting the waste oil, and blowing the residual waste oil in a pipeline into the reaction kettle by using compressed air after the input of the waste oil is finished so as to prevent the pipeline from being blocked; controlling the oil temperature in the reaction kettle at 65 ℃, reacting at a low temperature for 110min, standing for 40min, opening a valve at the bottom of the reaction kettle to discharge acid residue water, and collecting the acid residue water to enter an acid residue water storage tank; in the step, the using amount of the methanol is 20% of the weight of the waste oil, and the using amount of the concentrated sulfuric acid is 0.8% of the weight of the waste oil;
(2) esterification reaction: heating the oil temperature in the reaction kettle to 105 ℃, starting to supplement methanol into the reaction kettle under the stirring condition, controlling the flow rate of the methanol to be 700L/h, controlling the oil temperature to be about 110 ℃ in the methanol supplementing process, starting to detect the acid value after supplementing the methanol for half an hour, detecting once every half an hour until the acid value of the oil in the reaction kettle is less than 3mgKOH/g, cooling, stopping supplementing the methanol, opening a valve at the bottom of the reaction kettle to discharge acid residue water, and collecting the acid residue water to enter an acid residue water storage tank; generally, 3.5 to 4 hours are needed from the beginning of alcohol supplement to the end of esterification;
(3) ester exchange reaction: when the temperature of oil in the reaction kettle is reduced to 85 ℃, adding methanol alkali which is formed by mixing sodium hydroxide and methanol into the reaction kettle, controlling the temperature of oil at 70 ℃, and carrying out transesterification reaction for 1.5 hours under the stirring condition, wherein the pH value of the transesterification reaction is controlled to be 7.5-8; after the reaction is finished, stopping stirring, separating the reaction product to obtain crude glycerol and crude methyl ester, and feeding the crude glycerol into a crude glycerol storage tank; in the step, the using amount of the methanol is 20 percent of the weight of the waste oil, and the using amount of the sodium hydroxide is 0.7 percent of the weight of the waste oil;
(4) flash evaporation dealcoholization: the crude methyl ester enters a flash evaporator for flash evaporation and methanol removal, and the temperature of the flash evaporation and methanol removal is controlled at 80 ℃;
(5) washing with water: feeding the crude methyl ester subjected to flash evaporation and dealcoholization into a water washing tank, controlling the temperature of the crude methyl ester to be 75 ℃ during water washing, controlling the using amount of water for water washing to be 20 percent of the weight of the crude methyl ester, controlling the water temperature to be 85 ℃, and carrying out water washing for 15 min; standing for 3 hours for layering, and discharging a lower water layer;
(6) deodorizing: deodorizing the washed crude methyl ester in a deodorizer;
(7) and (3) distillation: distilling the deodorized crude methyl ester in a methyl ester distillation tower, controlling the temperature at the bottom of the tower to be 235 ℃, the temperature at the middle part of the tower to be 215 ℃, the temperature at the top of the tower to be 100 ℃, and the vacuum degree to be 0.097Mpa, condensing the distilled methyl ester by a condenser to obtain a finished product of the biodiesel, wherein the acid value of the finished product is 0.40 mgKOH/g, and the yield is 87%;
collecting methanol overflowing from the top of the reaction kettle in the step (1) to the step (3) and methanol overflowing from the top of the flash evaporator in the step (4) to a methanol rectifying tower, rectifying and condensing the methanol in the methanol rectifying tower to obtain methanol with the concentration of more than 98 percent, and sending the methanol to a methanol raw material tank to be reused as the methanol raw material in the step (1) to the step (3);
conveying the acid residue water in the acid residue water storage tank in the step (1) and the crude glycerin in the crude glycerin storage tank in the step (3) to a neutralization kettle for neutralization reaction, evaporating methanol after the neutralization is finished, and conveying the evaporated methanol to a methanol rectifying tower; adding concentrated sulfuric acid to adjust the pH value of the neutralized product after the methanol removal to 6-6.5, standing and layering for about 5 hours, wherein the lower layer of glycerol enters a glycerol storage tank, and the upper layer of acidified oil enters a waste oil storage tank to be reused as a raw material.
Example 3:
the green production process of the biodiesel shown in figure 1 comprises the following steps:
(1) pre-esterification: sequentially inputting methanol, concentrated sulfuric acid (98% sulfuric acid, commercially available) and waste oil (swill-cooked dirty oil) into a reaction kettle, heating the reaction kettle while stirring when inputting the waste oil, and blowing the residual waste oil in a pipeline into the reaction kettle by using compressed air after the input of the waste oil is finished so as to prevent the pipeline from being blocked; controlling the oil temperature in the reaction kettle at 62 ℃, reacting at a low temperature for 120min, standing for 35min, opening a valve at the bottom of the reaction kettle to discharge acid residue water, and collecting the acid residue water to enter an acid residue water storage tank; in the step, the using amount of the methanol is 19% of the weight of the waste oil, and the using amount of the concentrated sulfuric acid is 0.5% of the weight of the waste oil;
(2) esterification reaction: heating the oil temperature in the reaction kettle to 100 ℃, starting to supplement methanol into the reaction kettle under the stirring condition, controlling the flow rate of the methanol to be 500L/h, controlling the oil temperature to be about 110 ℃ in the methanol supplementing process, starting to detect the acid value after supplementing the methanol for half an hour, detecting once every half an hour until the acid value of the oil in the reaction kettle is less than 3mgKOH/g, cooling, stopping supplementing the methanol, opening a valve at the bottom of the reaction kettle to discharge acid residue water, and collecting the acid residue water to enter an acid residue water storage tank; generally, 3.5 to 4 hours are needed from the beginning of alcohol supplement to the end of esterification;
(3) ester exchange reaction: when the temperature of oil in the reaction kettle is reduced to 80 ℃, adding methanol alkali which is formed by mixing sodium hydroxide and methanol into the reaction kettle, controlling the temperature of oil to be about 68 ℃, and carrying out transesterification reaction for 2 hours under the stirring condition, wherein the pH value of the transesterification reaction is controlled to be 7.5-8; after the reaction is finished, stopping stirring, separating the reaction product to obtain crude glycerol and crude methyl ester, and feeding the crude glycerol into a crude glycerol storage tank; in the step, the using amount of the methanol is 18 percent of the weight of the waste oil, and the using amount of the sodium hydroxide is 0.5 percent of the weight of the waste oil;
(4) flash evaporation dealcoholization: the crude methyl ester enters a flash evaporator for flash evaporation and methanol removal, and the temperature of the flash evaporation and methanol removal is controlled at 75 ℃;
(5) washing with water: feeding the crude methyl ester subjected to flash evaporation and dealcoholization into a water washing tank, controlling the temperature of the crude methyl ester to be 70 ℃ during water washing, controlling the using amount of water for water washing to be 18 percent of the weight of the crude methyl ester, controlling the water temperature to be 80 ℃, and carrying out water washing for 18 min; standing for 2.5 hours for layering, and discharging a lower water layer;
(6) deodorizing: deodorizing the washed crude methyl ester in a deodorizer;
(7) and (3) distillation: distilling the deodorized crude methyl ester in a methyl ester distillation tower, controlling the temperature at the bottom of the tower to be 235 ℃, the temperature at the middle part of the tower to be 215 ℃, the temperature at the top of the tower to be 100 ℃, and the vacuum degree to be 0.095Mpa, condensing the distilled methyl ester by a condenser to obtain a finished product of the biodiesel, wherein the acid value of the finished product is 0.32 mgKOH/g, and the yield is 91%;
collecting methanol overflowing from the top of the reaction kettle in the step (1) to the step (3) and methanol overflowing from the top of the flash evaporator in the step (4) to a methanol rectifying tower, rectifying and condensing the methanol in the methanol rectifying tower to obtain methanol with the concentration of more than 98 percent, and sending the methanol to a methanol raw material tank to be reused as the methanol raw material in the step (1) to the step (3);
conveying the acid residue water in the acid residue water storage tank in the step (1) and the crude glycerin in the crude glycerin storage tank in the step (3) to a neutralization kettle for neutralization reaction, evaporating methanol after the neutralization is finished, and conveying the evaporated methanol to a methanol rectifying tower; adding concentrated sulfuric acid to adjust the pH value of the neutralized product after the methanol removal to 6-6.5, standing and layering for about 5 hours, wherein the lower layer of glycerol enters a glycerol storage tank, and the upper layer of acidified oil enters a waste oil storage tank to be reused as a raw material.
In comparison, according to the conventional production process, namely the operation of not recovering the acidified oil, the yield of the produced biodiesel is only about 80 percent, and the process yield is obviously improved.
The above-described embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention in any way, and other variations and modifications may be made without departing from the spirit of the invention as set forth in the claims.
Claims (7)
1. The green production process of the biodiesel is characterized by comprising the following steps of:
(1) pre-esterification: sequentially inputting methanol, concentrated sulfuric acid and waste oil into a reaction kettle, heating the reaction kettle while stirring when the waste oil is input, and blowing the residual waste oil in the pipeline into the reaction kettle by using compressed air so as to prevent the pipeline from being blocked after the waste oil is input; controlling the oil temperature in the reaction kettle at 60-65 ℃, reacting at low temperature for 110-130min, standing for 30-40min, opening a valve at the bottom of the reaction kettle to discharge acid residue water, and collecting the acid residue water to enter an acid residue water storage tank;
(2) esterification reaction: heating the oil temperature in the reaction kettle to 100-plus 105 ℃, starting to supplement methanol into the reaction kettle under the stirring condition, controlling the oil temperature to be between 108-plus 112 ℃ in the methanol supplementing process until the acid value of the oil in the reaction kettle is less than 3mgKOH/g, cooling, stopping supplementing the methanol, opening a valve at the bottom of the reaction kettle to discharge acid residue water, collecting the acid residue water, and feeding the acid residue water into an acid residue water storage tank;
(3) ester exchange reaction: when the temperature of oil in the reaction kettle is reduced to 80-85 ℃, adding methanol alkali into the reaction kettle, wherein the methanol alkali is formed by mixing sodium hydroxide and methanol, controlling the temperature of grease to be 65-70 ℃, carrying out ester exchange reaction for 1.5-2 hours under the condition of stirring, stopping stirring after the reaction is finished, separating a reaction product to obtain crude glycerol and crude methyl ester, and feeding the crude glycerol into a crude glycerol storage tank;
(4) flash evaporation dealcoholization: the crude methyl ester enters a flash evaporator for flash evaporation and methanol removal, and the temperature of the flash evaporation and methanol removal is controlled to be 75-80 ℃;
(5) washing with water: feeding the crude methyl ester subjected to flash evaporation and dealcoholization into a water washing tank, controlling the temperature of the crude methyl ester to be 70-75 ℃ during water washing, standing for 2-3 hours for layering, and discharging a lower water layer;
(6) deodorizing: deodorizing the washed crude methyl ester in a deodorizer;
(7) and (3) distillation: the deodorized crude methyl ester enters a methyl ester distillation tower for distillation, and the distilled methyl ester is condensed by a condenser to obtain a finished product of the biodiesel;
collecting methanol overflowing from the top of the reaction kettle in the step (1) to the step (3) and methanol overflowing from the top of the flash evaporator in the step (4) to a methanol rectifying tower, rectifying and condensing the methanol in the methanol rectifying tower to obtain methanol with the concentration of more than 98 percent, and sending the methanol to a methanol raw material tank to be reused as the methanol raw material in the step (1) to the step (3);
conveying the acid residue water in the acid residue water storage tank in the step (1) and the crude glycerin in the crude glycerin storage tank in the step (3) to a neutralization kettle for neutralization reaction, evaporating methanol after the neutralization is finished, and conveying the evaporated methanol to a methanol rectifying tower; adding concentrated sulfuric acid to adjust the pH value of the neutralized product subjected to methanol removal to 6-6.5, standing for layering, allowing the lower layer of glycerol to enter a glycerol storage tank, and allowing the upper layer of acidified oil to enter a waste oil storage tank to be reused as a raw material;
in the step (1), the using amount of the methanol is 18-20% of the weight of the waste oil; in the step (1), the dosage of the concentrated sulfuric acid is 0.3-0.8% of the weight of the waste grease.
2. The green production process of biodiesel according to claim 1, characterized in that: in the step (2), the flow rate of methanol is controlled to be 300-700L/h during methanol supplement.
3. The green production process of biodiesel according to claim 1, characterized in that: in the step (3), the dosage of the methanol is 15-20% of the weight of the waste oil, and the dosage of the sodium hydroxide is 0.3-0.7% of the weight of the waste oil.
4. The green production process of biodiesel according to claim 1, characterized in that: in the step (3), the pH of the ester exchange reaction is controlled to be 7.5-8.
5. The green production process of biodiesel according to claim 1, characterized in that: in the step (5), the dosage of washing water is 15-20% of the weight of the crude methyl ester, the water temperature is 80-85 ℃, and the washing time is 15-20 min.
6. The green production process of biodiesel according to claim 1, characterized in that: in the step (7), the methyl ester distillation is carried out under the negative pressure which is controlled to be more than-0.095 MPa.
7. The green production process of biodiesel according to claim 1, characterized in that: in step (7), the methyl ester distillation temperature is 215-235 ℃.
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